1 Introduction

1.1 Processes and threads: in underlying OS and in Windows

Before going into the depths of debugging in Wine, here's a small overview of process and thread handling in Wine. It has to be clear that there are two different beasts: processes/threads from the Unix point of view and processes/threads from a Windows point of view.

Each Windows thread is implemented as a Unix thread, meaning that all threads of a same Windows process share the same (unix) address space.

In the following:

W-process means a process in Windows terminology

U-process means a process in Unix terminology

W-thread means a thread in Windows terminology

A W-process is made of one or several W-threads. Each W-thread is mapped to one and only one U-process. All U-processes of a same W-process share the same address space.

Each Unix process can be identified by two values:

the Unix process id (upid in the following)

the Windows thread id (tid)

Each Windows process has also a Windows process id (wpid in the following). It must be clear that upid and wpid are different and shall not be used instead of the other.

Wpid and tid are defined (Windows) system wide. They must not be confused with process or thread handles which, as any handle, are indirections to system objects (in this case processes or threads). A same process can have several different handles on the same kernel object. The handles can be defined as local (the values is only valid in a process), or system wide (the same handle can be used by any W-process).

1.2 Wine, debugging and WineDbg

When talking of debugging in Wine, there are at least two levels to think of:

the Windows debugging API.

the Wine integrated debugger, dubbed winedbg.

Wine implements most of the Windows debugging API. The first part of the debugging APIs (in KERNEL32.DLL) allows a W-process, called the debugger, to control the execution of another W-process, the debuggee. To control means stopping/resuming execution, enabling/disabling single stepping, setting breakpoints, reading/writing debuggee memory... Another part of the debugging APIs resides in DBGHELP.DLL (and its ancestor IMAGEHLP.DLL) and lets a debugger look into symbols and types from any module (if the module has been compiled with the proper options).

winedbg is a Winelib application making use of these APIs (KERNEL32.DLL debugging API and class="libraryfile"DBGHELP.DLL) to allow debugging both any Wine or Winelib application as well as Wine itself (kernel and all DLLs).

2 WineDbg modes of invocation

2.1 Starting a process

Any application (either a Windows native executable, or a Winelib application) can be run through winedbg. Command line options and tricks are the same as for wine:

winedbg telnet.exe
winedbg hl.exe -windowed

2.2 Attaching

winedbg can also be launched without any command line argument: winedbg is started without any attached process. You can get a list of running W-processes (and their wpid) using the info process command, and then, with the attach command, pick up the wpid of the W-process you want to debug. This is a neat feature as it allows you to debug an already started application.

2.3 On exceptions

When an exception occurs, Wine checks if the W-process is debugged. If so, the exception event is sent to the debugger, which takes care of it: end of the story. This mechanism is part of the standard Windows debugging API.

If the W-process is not debugged, Wine tries to launch a debugger. This debugger (normally winedbg, see III Configuration for more details), at startup, attaches to the W-process which generated the exception event. In this case, you are able to look at the causes of the exception, and either fix the causes (and continue further the execution) or dig deeper to understand what went wrong.

If winedbg is the standard debugger, the pass and cont commands are the two ways to let the process go further for the handling of the exception event.

To be more precise on the way Wine (and Windows) generates exception events, when a fault occurs (segmentation violation, stack overflow...), the event is first sent to the debugger (this is known as a first chance exception). The debugger can give two answers:

continue

the debugger had the ability to correct what's generated the exception, and is now able to continue process execution.

pass

the debugger couldn't correct the cause of the first chance exception. Wine will now try to walk the list of exception handlers to see if one of them can handle the exception. If no exception handler is found, the exception is sent once again to the debugger to indicate the failure of the exception handling.

Note: since some of Wine code uses exceptions and try/catch blocks to provide some functionality, winedbg can be entered in such cases with segv exceptions. This happens, for example, with IsBadReadPtr function. In that case, the pass command shall be used, to let the handling of the exception to be done by the catch block in IsBadReadPtr.

2.4 Interrupting

You can stop the debugger while it's running by hitting Ctrl+C in its window. This will stop the debugged process, and let you manipulate the current context.

2.5 Quitting

Wine supports the new XP APIs, allowing for a debugger to detach from a program being debugged (see detach command).

3 Using the Wine Debugger

This section describes where to start debugging Wine. If at any point you get stuck and want to ask for help, please read the How to Report A Bug section of the Wine Users Guide for information on how to write useful bug reports.

Steps to debug a crash. You may stop at any step, but please report the bug and provide as much of the information gathered to the bug report as feasible.

Get the reason for the crash. This is usually a page fault, an unimplemented function in Wine, or the like. When reporting a crash, report this whole crashdump even if it doesn't make sense to you.

(In this case it is page fault on write access to 0x00000000. Most likely Wine passed NULL to the application or the like.)

Determine the cause of the crash. Since this is usually a primary/secondary reaction to a failed or misbehaving Wine function, rerun Wine with the WINEDEBUG=+relay environment variable set. This will generate quite a lot of output, but usually the reason is located in the last calls. Those lines usually look like this:

If you have found a misbehaving Wine function, try to find out why it misbehaves. Find the function in the source code. Try to make sense of the arguments passed. Usually there is a WINE_DEFAULT_DEBUG_CHANNEL(channel); at the beginning of the source file. Rerun wine with the WINEDEBUG=+xyz,+relay environment variable set.

Occasionally there are additional debug channels defined at the beginning of the source file in the form WINE_DECLARE_DEBUG_CHANNEL(channel); if so the offending function may also use one of these alternate channels. Look through the the function for TRACE_(channel)("... /n"); and add any additional channels to the command line.

Additional information on how to debug using the internal debugger can be found in programs/winedbg/README.

If this information isn't clear enough or if you want to know more about what's happening in the function itself, try running wine with WINEDEBUG=+all, which dumps ALL included debug information in wine. It is often necessary to limit the debug output produced. That can be done by piping the output through grep, or alternatively with registry keys. See Section 1.5.3 for more information.

If even that isn't enough, add more debug output for yourself into the functions you find relevant. See The section on Debug Logging in this guide for more information. You might also try to run the program in gdb instead of using the Wine debugger. If you do that, use handle SIGSEGV nostop noprint to disable the handling of seg faults inside gdb (needed for Win16).

You can also set a breakpoint for that function. Start wine using winedbg instead of wine. Once the debugger is running enter break RegOpenKeyExW (replace by function you want to debug, case is relevant) to set a breakpoint. Then use continue to start normal program-execution. Wine will stop if it reaches the breakpoint. If the program isn't yet at the crashing call of that function, use continue again until you are about to enter that function. You may now proceed with single-stepping the function until you reach the point of crash. Use the other debugger commands to print registers and the like.

3.2 Program hangs, nothing happens

Start the program with winedbg instead of wine. When the program locks up switch to the winedbg terminal and press Ctrl+C. This will stop the program and let you debug the program as you would for a crash.

3.3 Program reports an error with a message box

Sometimes programs are reporting failure using more or less nondescript message boxes. We can debug this using the same method as Crashes, but there is one problem... For setting up a message box the program also calls Wine producing huge chunks of debug code.

Since the failure happens usually directly before setting up the message box you can start winedbg and set a breakpoint at MessageBoxA (called by win16 and win32 programs) and proceed with continue. With WINEDEBUG=+all Wine will now stop directly before setting up the message box. Proceed as explained above.

You can also run wine using WINEDEBUG=+relay wine program.exe 2>&1 | less -i and in less search for “MessageBox”.

3.4 Disassembling programs

You may also try to disassemble the offending program to check for undocumented features and/or use of them.

Disassembling win32 programs is possible using e.g. GoVest by Ansgar Trimborn. It can be found here.

You can also use the newer and better Interactive Disassembler (IDA) from DataRescue. Take a look in the AppDB for links to various versions of IDA.

Another popular disassembler is Windows Disassembler 32 from URSoft. Look for a file called w32dsm87.zip (or similar) on winsite.com or softpedia.com. It seems that Windows Disassembler 32 currently has problems working correctly under Wine, so use IDA or GoVest.

Also of considerable fame amongst disassemblers is SoftIce from NuMega. That software has since been acquired by CompuWare and made part of their Windows driver development suite. Newer versions of SoftIce needs to run as a Windows Service and therefore won't currently work under Wine.

If nothing works for you, you might try one of the disassemblers found in Google directory.

Understanding disassembled code is mostly a question of exercise. Most code out there uses standard C function entries (for it is usually written in C). Win16 function entries usually look like that:

This is a FAR function with no local storage. The arguments usually start at [bp+6] with increasing offsets. Note, that [bp+6] belongs to the rightmost argument, for exported win16 functions use the PASCAL calling convention. So, if we use strcmp(a,b) with a and b both 32-bit variables b would be at [bp+6] and a at [bp+10].

Most functions make also use of local storage in the stackframe:

enter0086,00...functioncode...leaveretfXXXX

This does mostly the same as above, but also adds 0x86 bytes of stackstorage, which is accessed using [bp-xx]. Before calling a function, arguments are pushed on the stack using something like this:

The code seems to find a writable harddisk and tries to create a file there. To work around this bug, you can define C: as a network drive, which is ignored by the code above.

3.6 Debugging Tips

Here are some additional debugging tips:

If you have a program crashing at such an early loader phase that you can't use the Wine debugger normally, but Wine already executes the program's start code, then you may use a special trick. You should do a

WINEDEBUG=+relay wine program

to get a listing of the functions the program calls in its start function. Now you do a

winedbg winfile.exe

This way, you get into winedbg. Now you can set a breakpoint on any function the program calls in the start function and just type c to bypass the eventual calls of Winfile to this function until you are finally at the place where this function gets called by the crashing start function. Now you can proceed with your debugging as usual.

If you try to run a program and it quits after showing an error message box, the problem can usually be identified in the return value of one of the functions executed before MessageBox(). That's why you should re-run the program with e.g.

WINEDEBUG=+relay wine program_name &>relmsg

Then do a more relmsg and search for the last occurrence of a call to the string "MESSAGEBOX". This is a line like

I think that the call to MessageBox() in this example is not caused by a wrong result value of some previously executed function (it's happening quite often like that), but instead the message box complains about a runtime error at 0x0004:0x1056.

As the segment value of the address is only 4, I think that that is only an internal program value. But the offset address reveals something quite interesting: offset 1056 is very close to the return address of FREELIBRARY():

Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff
^^^^

Provided that segment 0x0004 is indeed segment 0x1cf, we now we can use IDA to disassemble the part that caused the error. We just have to find the address of the call to FreeLibrary(). Some lines before that the runtime error occurred. But be careful! In some cases you don't have to disassemble the main program, but instead some DLL called by it in order to find the correct place where the runtime error occurred. That can be determined by finding the origin of the segment value (in this case 0x1cf).

If you have created a relay file of some crashing program and want to set a breakpoint at a certain location which is not yet available as the program loads the breakpoint segment during execution, you may set a breakpoint to GetVersion16/32 as those functions are called very often.

Then do a c until you are able to set this breakpoint without error message.

3.7 Some basic debugger usages

After starting your program with

winedbg myprog.exe

the program loads and you get a prompt at the program starting point. Then you can set breakpoints:

b RoutineName (by routine name) OR
b *0x812575 (by address)

Then you hit c (continue) to run the program. It stops at the breakpoint. You can type

step (to step one line) OR
stepi (to step one machine instruction at a time;
here, it helps to know the basic 386
instruction set)
info reg (to see registers)
info stack (to see hex values in the stack)
info local (to see local variables)
list line number (to list source code)
x variable name (to examine a variable; only works if code
is not compiled with optimization)
x 0x4269978 (to examine a memory location)
? (help)
q (quit)

4 Useful memory addresses

Wine uses several different kinds of memory addresses.

Win32/“normal” Wine addresses/Linux: linear addresses.

Linear addresses can be everything from 0x0 up to 0xffffffff. In Wine on Linux they are often around e.g. 0x08000000, 0x00400000 (std. Win32 program load address), 0x40000000. Every Win32 process has its own private 4GB address space (that is, from 0x0 up to 0xffffffff).

Win16 “enhanced mode”: segmented addresses.

These are the “normal” Win16 addresses, called SEGPTR. They have a segment:offset notation, e.g. 0x01d7:0x0012. The segment part usually is a “selector”, which always has the lowest 3 bits set. Some sample selectors are 0x1f7, 0x16f, 0x8f. If these bits are set except for the lowest bit, as e.g. with 0x1f6,xi then it might be a handle to global memory. Just set the lowest bit to get the selector in these cases. A selector kind of “points” to a certain linear (see above) base address. It has more or less three important attributes: segment base address, segment limit, segment access rights.

Example:

Selector 0x1f7 (0x40320000, 0x0000ffff, r-x) So 0x1f7 has a base address of 0x40320000, the segment's last address is 0x4032ffff (limit 0xffff), and it's readable and executable. So an address of 0x1f7:0x2300 would be the linear address of 0x40322300.

DOS/Win16 “standard mode”

They, too, have a segment:offset notation. But they are completely different from “normal” Win16 addresses, as they just represent at most 1MB of memory: the segment part can be anything from 0 to 0xffff, and it's the same with the offset part.

Now the strange thing is the calculation that's behind these addresses: just calculate segment*16 + offset in order to get a “linear DOS” address. So e.g. 0x0f04:0x3628 results in 0xf040 + 0x3628 = 0x12668. And the highest address you can get is 0xfffff (1MB), of course.

5 Configuration

5.1 Windows Debugging configuration

The Windows debugging API uses a registry entry to know which debugger to invoke when an unhandled exception occurs (see On exceptions for some details). Two values in key

[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug]

determine the behavior:

Debugger

This is the command line used to launch the debugger (it uses two printf formats (%ld) to pass context dependent information to the debugger). You should put here a complete path to your debugger (winedbg can of course be used, but any other Windows debugging API aware debugger will do). The path to the debugger you choose to use must be reachable via one of the DOS drives configured under /dosdevices in your WINEPREFIX or ~/.wine folder.

Auto

If this value is zero, a message box will ask the user if he/she wishes to launch the debugger when an unhandled exception occurs. Otherwise, the debugger is automatically started.

Note 1: Creating this key is mandatory. Not doing so will not fire the debugger when an exception occurs.

Note 2: wineinstall (available in Wine source) sets up this correctly. However, due to some limitation of the registry installed, if a previous Wine installation exists, it's safer to remove the whole

[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug]

key before running again wineinstall to regenerate this key.

5.2 WineDbg configuration

winedbg can be configured through a number of options. Those options are stored in the registry, on a per user basis. The key is (in my registry)

[HKCU\\Software\\Wine\\WineDbg]

Those options can be read/written while inside winedbg, as part of the debugger expressions. To refer to one of these options, its name must be prefixed by a $ sign. For example,

set $BreakAllThreadsStartup = 1

sets the option BreakAllThreadsStartup to TRUE.

All the options are read from the registry when winedbg starts (if no corresponding value is found, a default value is used), and are written back to the registry when winedbg exits (hence, all modifications to those options are automatically saved when winedbg terminates).

Here's the list of all options:

BreakAllThreadsStartup

Set to TRUE if at all threads start-up the debugger stops set to FALSE if only at the first thread startup of a given process the debugger stops. FALSE by default.

BreakOnCritSectTimeOut

Set to TRUE if the debugger stops when a critical section times out (5 minutes); TRUE by default.

BreakOnAttach

Set to TRUE if when winedbg attaches to an existing process after an unhandled exception, winedbg shall be entered on the first attach event. Since the attach event is meaningless in the context of an exception event (the next event which is the exception event is of course relevant), that option is likely to be FALSE.

BreakOnFirstChance

An exception can generate two debug events. The first one is passed to the debugger (known as a first chance) just after the exception. The debugger can then decide either to resume execution (see winedbg's cont command) or pass the exception up to the exception handler chain in the program (if it exists) (winedbg implements this through the pass command). If none of the exception handlers takes care of the exception, the exception event is sent again to the debugger (known as last chance exception). You cannot pass on a last exception. When the BreakOnFirstChance exception is TRUE, then winedbg is entered for both first and last chance exceptions (to FALSE, it's only entered for last chance exceptions).

AlwaysShowThunk

Set to TRUE if the debugger, when looking up for a symbol from its name, displays all the thunks with that name. The default value (FALSE) allows not to have to choose between a symbol and all the import thunks from all the DLLs using that symbols.

5.3 Configuring +relay behaviour

When setting WINEDEBUG to +relay and debugging, you might get a lot of output. You can limit the output by configuring the value RelayExclude in the registry, located under the key [HKCU\\Software\\Wine\\Debug]

Set the value of RelayExclude to a semicolon-separated list of calls to exclude, e.g. "RtlEnterCriticalSection;RtlLeaveCriticalSection;kernel32.97;kernel32.98".

RelayInclude is an option similar to RelayExclude, except that functions listed here will be the only ones included in the output.

If your application runs too slow with +relay to get meaningful output and you're stuck with multi-GB relay log files, but you're not sure what to exclude, here's a trick to get you started. First, run your application for a minute or so, piping its output to a file on disk:

Exclude the bottom-most calls with RelayExclude after making sure that they are irrelevant, then run your application again.

6 WineDbg Expressions and Variables

6.1 Expressions

Expressions in Wine Debugger are mostly written in a C form. However, there are a few discrepancies:

Identifiers can take a '!' in their names. This allow mainly to access symbols from different DLLs like USER32!CreateWindowExA.

In cast operation, when specifying a structure or an union, you must use the struct or union keyword (even if your program uses a typedef).

When specifying an identifier by its name, if several symbols with the same name exist, the debugger will prompt for the symbol you want to use. Pick up the one you want from its number.

In lots of cases, you can also use regular expressions for looking for a symbol.

winedbg defines its own set of variables. The configuration variables from above are part of them. Some others include:

$ThreadId

ID of the W-thread currently examined by the debugger

$ProcessId

ID of the W-thread currently examined by the debugger

registers

All CPU registers are also available, using '$' as a prefix. You can use info regs to get a list of available CPU registers.

The $ThreadId and $ProcessId variables can be handy to set conditional breakpoints on a given thread or process.

7 WineDbg Command Reference

7.1 Misc

Table 1-1. WineDbg misc. commands

abort

aborts the debugger

quit

exits the debugger

attachN

attach to a W-process (N is its ID, numeric or hexadecimal (0xN)). IDs can be obtained using the info process command. Note the info process command returns hexadecimal values.

detach

detach from a W-process.

help

prints some help on the commands

help info

prints some help on info commands

7.2 Flow control

Table 1-2. WineDbg flow control commands

cont, c

continue execution until next breakpoint or exception.

pass

pass the exception event up to the filter chain.

step, s

continue execution until next “C” line of code (enters function call)

next, n

continue execution until next “C” line of code (doesn't enter function call)

stepi, si

execute next assembly instruction (enters function call)

nexti, ni

execute next assembly instruction (doesn't enter function call)

finish, f

execute until current function is exited

cont, step, next, stepi, nexti can be postfixed by a number (N), meaning that the command must be executed N times.

7.3 Breakpoints, watch points

Table 1-3. WineDbg break & watch points

enableN

enables (break|watch)point N

disableN

disables (break|watch)point N

deleteN

deletes (break|watch)point N

condN

removes any existing condition to (break|watch)point N

condN expr

adds condition expr to (break|watch)point N. expr will be evaluated each time the breakpoint is hit. If the result is a zero value, the breakpoint isn't triggered.

break *N

adds a breakpoint at address N

breakid

adds a breakpoint at the address of symbol id

breakid N

adds a breakpoint at line N inside symbol id

breakN

adds a breakpoint at line N of current source file

break

adds a breakpoint at current $PC address

watch *N

adds a watch command (on write) at address N (on 4 bytes)

watchid

adds a watch command (on write) at the address of symbol id

info break

lists all (break|watch)points (with state)

You can use the symbol EntryPoint to stand for the entry point of the DLL.

When setting a break/watch-point by id, if the symbol cannot be found (for example, the symbol is contained in a not yet loaded module), winedbg will recall the name of the symbol and will try to set the breakpoint each time a new module is loaded (until it succeeds).

7.4 Stack manipulation

Table 1-4. WineDbg stack manipulation

bt

print calling stack of current thread

bt N

print calling stack of thread of ID N (note: this doesn't change the position of the current frame as manipulated by the up and dn commands)

You can specify the end target (to change the 10 lines value) using the ','. For example:

Table 1-6. WineDbg list command examples

list 123, 234

lists source lines from line 123 up to line 234 in current file

list foo.c:1, 56

lists source lines from line 1 up to 56 in file foo.c

7.6 Displaying

A display is an expression that's evaluated and printed after the execution of any winedbg command.

winedbg will automatically detect if the expression you entered contains a local variable. If so, display will only be shown if the context is still in the same function as the one the debugger was in when the display expression was entered.

Table 1-7. WineDbg displays

info display

lists the active displays

display

print the active displays' values (as done each time the debugger stops)

displayexpr

adds a display for expression expr

display /fmt expr

adds a display for expression expr. Printing evaluated expr is done using the given format (see print command for more on formats)

del displayN, undisplayN

deletes display N

7.7 Disassembly

Table 1-8. WineDbg dissassembly

disas

disassemble from current position

disasexpr

disassemble from address expr

disasexpr, expr

disassembles code between addresses specified by the two exprs

7.8 Memory (reading, writing, typing)

Table 1-9. WineDbg memory management

xexpr

examines memory at expr address

x /fmt expr

examines memory at expr address using format fmt

printexpr

prints the value of expr (possibly using its type)

print /fmt expr

prints the value of expr using format fmt

setlval=expr

writes the value of expr in lval

whatisexpr

prints the C type of expression expr

set ! symbol_picker interactive

when printing a value, if several symbols are found, ask the user which one to pick (default)

set ! symbol_picker scopedb

when printing a value, give precedence to local symbols over global symbols

fmt is either letter or count letter (without a space between count and letter), where letter can be

s an ASCII string

u a Unicode UTF16 string

i instructions (disassemble)

x 32-bit unsigned hexadecimal integer

d 32-bit signed decimal integer

w 16-bit unsigned hexadecimal integer

c character (only printable 0x20-0x7f are actually printed)

b 8-bit unsigned hexadecimal integer

g GUID

7.9 Information on Wine internals

Table 1-10. WineDbg Win32 objects management

info class

lists all Windows classes registered in Wine

info classid

prints information on Windows class id

info share

lists all the dynamic libraries loaded in the debugged program (including .so files, NE and PE DLLs)

info shareN

prints information on module at address N

info regs

prints the value of the CPU registers

info all-regs

prints the value of the CPU and Floating Point registers

info segmentN

prints information on segment N (i386 only)

info segment

lists all allocated segments (i386 only)

info stack

prints the values on top of the stack

info map

lists all virtual mappings used by the debugged program

info mapN

lists all virtual mappings used by the program of wpid N

info wndN

prints information of Window of handle N

info wnd

lists all the window hierarchy starting from the desktop window

info process

lists all w-processes in Wine session

info thread

lists all w-threads in Wine session

info exception

lists the exception frames (starting from current stack frame)

7.10 Debug channels

It is possible to turn on and off debug messages as you are debugging using the set command (only for debug channels specified in WINEDEBUG environment variable). See Chapter 2 for more details on debug channels.

Table 1-11. WineDbg debug channels management

set + warnchannel

turn on warn on channel

set +channel

turn on warn/fixme/err/trace on channel

set -channel

turn off warn/fixme/err/trace on channel

set - fixme

turn off the “fixme” class

8 Other debuggers

8.1 GDB mode

WineDbg can act as a remote monitor for GDB. This allows to use all the power of GDB, but while debugging wine and/or any Win32 application. To enable this mode, just add --gdb to winedbg command line. You'll end up on a GDB prompt. You'll have to use the GDB commands (not WineDbg ones).

However, some limitation in GDB while debugging wine (see below) don't appear in this mode:

Moreover, it also provides support for the Dwarf II debug format (which became the default format (instead of stabs) in gcc 3.1).

A few Wine extensions available through the monitor command.

Table 1-12. WineDbg debug channels management

monitor wnd

lists all window in the Wine session

monitor proc

lists all processes in the Wine session

monitor mem

displays memory mapping of debugged process

8.2 Graphical frontends to gdb

This section will describe how you can debug Wine using the GDB mode of winedbg and some graphical front ends to GDB for those of you who really like graphical debuggers.

8.2.1 DDD

Use the following steps, in this order:

Start the Wine debugger with a command line like:

winedbg --gdb --no-start name_of_exe_to_debug.exe optional parameters

Start ddd

In ddd, use Open File or Open Program to point to the Wine executable.

In the output of above command, there's a line like

target remote localhost:12345

Copy that line and paste into ddd command pane (the one with the (gdb) prompt)

The program should now be loaded and up and running.

8.2.2 kdbg

Use the following steps, in this order:

Start the Wine debugger with a command line like:

winedbg --gdb --no-start name_of_exe_to_debug.exe optional parameters

In the output of above command, there's a line like

target remote localhost:12345

Start kdbg with

kdbg -r localhost:12345 wine

localhost:12345 is not a fixed value, but has been printed in first step. “wine” should also be the full path to the Wine executable.

The program should now be loaded and up and running.

8.3 Using other Unix debuggers

You can also use other debuggers (like gdb), but you must be aware of a few items:

You need to attach the unix debugger to the correct unix process (representing the correct windows thread) (you can “guess” it from a ps fax command for example. When running the emulator, usually the first two upids are for the Windows application running the desktop, the first thread of the application is generally the third upid; when running a Winelib program, the first thread of the application is generally the first upid)

Note: If you plan to used gdb for a multi-threaded Wine application (native or Winelib), then gdb will be able to handle the multiple threads directly only if:

Wine is running on the pthread model (it won't work in the kthread one). See the Wine architecture documentation for further details.

gdb supports the multi-threading (you need at least version 5.0 for that).

In the unfortunate case (no direct thread support in gdb because one of the above conditions is false), you'll have to spawn a different gdb session for each Windows thread you wish to debug (which means no synchronization for debugging purposes between the various threads).

Here's how to get info about the current execution status of a certain Wine process:

Change into your Wine source dir and enter:

$ gdb wine

Switch to another console and enter ps ax | grep wine to find all wine processes. Inside gdb, repeat for all Wine processes:

(gdb) attach wpid

with wpid being the process ID of one of the Wine processes. Use

(gdb) bt

to get the backtrace of the current Wine process, i.e. the function call history. That way you can find out what the current process is doing right now. And then you can use several times:

(gdb) n

or maybe even

(gdb) b SomeFunction

and

(gdb) c

to set a breakpoint at a certain function and continue up to that function. Finally you can enter

(gdb) detach

to detach from the Wine process.

8.4 Using other Windows debuggers

You can use any Windows debugging API compliant debugger with Wine. Some reports have been made of success with VisualStudio debugger (in remote mode, only the hub runs in Wine). GoVest fully runs in Wine.

8.5 Main differences between winedbg and regular Unix debuggers

Table 1-13. Debuggers comparison

WineDbg

gdb

WineDbg debugs a Windows process: the various threads will be handled by the same WineDbg session, and a breakpoint will be triggered for any thread of the W-process

gdb debugs a Windows thread: a separate gdb session is needed for each thread of a Windows process and a breakpoint will be triggered only for the w-thread debugged